1. Field
Aspects of the present invention generally relate to detecting vehicle queues and more specifically relate to a connected vehicle system and a method for precisely determining a vehicle queue length based on the number of vehicles that are stopped in a vehicle queue at a traffic light signal.
2. Description of the Related Art
Connected vehicles are becoming a reality, which takes driver assistance towards its logical goal: a fully automated network of cars aware of each other and their environment. A connected vehicle system makes mobility safer by connecting cars to everything.
Vehicular communications systems are networks in which vehicles and roadside units (RSUs) are the communicating nodes, providing each other with information, such as safety warnings and traffic information. They can be effective in avoiding accidents and traffic congestion. Both types of nodes are generally dedicated short-range communications (DSRC) devices. DSRC works in 5.9 GHz band with bandwidth of 75 MHz and approximate range of 1000 m.
Vehicular communications systems are usually developed as a part of intelligent transportation systems (ITS). For example, a Vehicle to Vehicle (V2V) communications system is an automobile technology designed to allow automobiles to “talk” to each other. These systems generally use a region of the 5.9 GHz band set aside by the United States Congress in 1999, the unlicensed frequency also used by Wi-Fi. The V2V communications system is currently in active development by many car makers.
Traffic control devices cannot precisely determine the number of vehicles that are stopped in queues. U.S. Pat. No. 8,386,156 describes a system and method for lane-specific vehicle detection and control. U.S. Patent Application Publication No. 2012/0029798 describes a vehicle detection method using On-Board Units (OBUs) that transmit vehicle location, direction heading and speed multiple times per second. Used in conjunction, the two technologies can provide traffic signal controllers with a precise arrival time for each vehicle.
This problem of how to precisely determine the number of vehicles that are stopped in queues is solved up to now by following ways: a) Loop Detectors: a single bit indicates that one or more metallic objects occupy the loop, b) Video Detectors: a single bit per each moving objects within the camera field of view, c) Radar Detector: it indicates vehicle approach and velocity, d) Magnetometers: a single bit indicates that a vehicle occupies the magnetic sensor, and e) On-board Unit (OBU): a vehicle transmits location, direction heading and speed 10 times per second.
However, public budgets often leave detection devices in disrepair or inoperable due to adverse weather conditions than can blind optical systems, such as video detectors. The effectiveness of the two technologies of lane-specific vehicle detection, control and use of On-Board Units (OBUs) is relative to the penetration of vehicles equipped with OBUs, which may take years to reach a significant percentage of total traffic volume.
Therefore, there is a need for improvements in vehicle queue length detection for efficiently controlling traffic light signals.